1. Field of the Invention
The present invention relates to a starting element, a gearbox and a drivetrain having the starting element.
2. Description of the Prior Art
Starting elements are used in a great variety of forms in the vehicle domain, particularly in the domain of motor vehicles. In these domains, they are often utilized within the framework of a drivetrain in a vehicle of this type for transmitting torque, for example, between a drive unit, i.e. an engine, and a downstream gearbox. This allows the drivetrain to be disconnected so that the engine can continue running, for example, when the vehicle is at a standstill.
Starting elements can also be used in other configurations in the drivetrain of a vehicle. For example, in hybrid drives they can be used between two different drive units or for alternately disconnecting and connecting different drive units with respect to a transmission input shaft. Starting elements can be used in connection with different drive unit technologies, i.e., internal combustion engines and electric motors, and in conjunction with various transmission engineering.
Starting elements usually comprise a friction clutch that often relies on the creation of a frictionally engaging contact between corresponding structural component parts coupled with an input component part and an output component part of the relevant clutch. The starting elements often have a piston or other actuating element for actuating the friction clutch. The piston is usually acted upon by a hydraulic medium to actuate the friction clutch. The piston can be acted upon by the hydraulic medium via different conventional systems.
DE 10 2012 201 507 A1 is directed to a clutch arrangement as starting element, for example, for a drivetrain of a vehicle. A piston is acted upon by a hydraulic medium to actuate the clutch arrangement. The clutch arrangement is a three-line system or three-line type. For this purpose, an interior space of the clutch arrangement is divided into three regions, namely, a piston pressure space, a partial volume and a second volume; in axial direction, the piston pressure space lies between the partial volume and the second volume. The second volume is arranged on the drive side with respect to the piston pressure space. The piston pressure space is separated from the partial volume by a dividing wall and from the second volume by the piston. The piston pressure space is charged with the hydraulic medium via an inlet bore that represents a first of the three lines or channels. To enable a movement of the piston, the second volume is fluidically connected via a further feed channel. The feed channel thus allows hydraulic medium to flow in and out in case of movement of the piston and accordingly serves to compensate the corresponding volume. An inlet area is connected to an inlet for the hydraulic medium via some absent teeth in an inner toothing and a corresponding outer toothing, respectively, of a transmission input shaft. Not only is the second volume supplied with the liquid medium via the inlet area resulting from the missing teeth, the residual space is also fluidically connected via the inlet area and oil guiding lines integrated in a bearing. An inlet bore to the piston pressure space is separated from the inlet area by a seal. Accordingly, the inlet area is the second line. The liquid medium can exit the partial volume via corresponding oil guiding channels in a bearing and an outlet area. The outlet area is formed between a lower hub and a pump hub and is the third line. Accordingly, the three-line system is relatively complicated in term's of design, and a dividing wall and additional sealing elements are required to separate three spaces from one another.
FIG. 6 shows a schematic cross-sectional view through a conventional starting element 1. In starting element 1, a piston 3 can be fluidically connected by a two-line system, i.e., via only two oil lines, namely, an oil inlet line 6 and an oil outlet line 7. An interior space 2 of the starting element 1 is divided by the piston 3 and dividing wall 8 into a piston pressure space, a residual space 5, and a further volume 9. The residual space 5 is fluidically connected to the piston pressure space 4 via a choke 10. The object of the choke 10 is to connect the oil inlet line 6 to the oil outlet line 7. The oil inlet line 6, which can also be designated as an inlet, opens into the piston pressure space, and the oil outlet line 7, which can also be designated as an outlet, opens into the residual space 5. Lines 6 and 7 cross one another so that the piston pressure space 4 can be connected to the oil inlet line 6 and the residual space 5 can be connected to oil outlet line 7. Naturally, the two lines 6 and 7 are nevertheless fluidically separated at a point where they cross one another. The fact that oil inlet line 6 and oil outlet line 7 cross one another can be attributed, for example, to a constructional type of oil pump in a gearbox to which the starting element 1 is coupled. It is undesirable for oil inlet line 6 and oil outlet line 7 to cross one another because special steps must then be taken at both the starting element 1 and the gearbox or oil pump, i.e., on the starting element side as well as on the gearbox side, to allow a connection. As further adaptation, a choke is inserted in the starting element 1 and a pressure is choked in the oil inlet line 6. Further, it is necessary to adapt a transmission input shaft in a front region and to adapt a torsion damper flange hub in order to provide sufficient space for lines 6 and 7 and for lines 6 and 7 to cross one another.